1. Field of the Invention
The present invention relates to a light guide plate and a support unit for the light guide plate to illuminate a liquid crystal panel as an image display body used in mobile phones and portable information terminals.
2. Description of the Prior Art
Display units such as a liquid crystal display have been using a backlight device to illuminate a display surface. The backlight device comprises a light guide plate installed at the back of the liquid crystal panel and a light source such as a light emitting diode (LED) or a cold-cathode tube arranged on one side of the light guide plate. Such a backlight device has an advantage of being able to reduce its overall thickness because the light source is arranged on one side of the light guide plate to emit light into the light guide plate from one side surface thereof. This construction in which the thin light guide plate receives light from its side, however, results in a poor light receiving efficiency.
Practices generally employed to improve the light receiving, efficiency involves enhancing an intensity of light emitted from the light source or arranging the light source close to the light guide plate. As disclosed in Japanese Patent Disclosure No. 7-114024, it has been proposed that a condenser lens be arranged between the light source and the side surface of the light guide plate to efficiently introduce light from the light source into the light guide plate.
In a backlight structure such as disclosed in the above official gazette, however, a separate condenser lens needs to be installed in the device, which increases not only the number of parts and the cost but also the number of manufacturing steps due to additional adjustments of shape and arrangement of the lens.
Further, a space required to accommodate the condenser lens limits a reduction in the thickness of the backlight device.
There is another problem. When light is introduced into the light guide plate from its side, brightness unevenness occurs in the light guide plate, with the brightness being highest at portions close to the light source and progressively decreasing with an increasing distance from the light source.
Further, conventional light guide plates are generally made of a hard material such as acrylic plate and shaped like a flat plate. Thus, it cannot illuminate a display with a curved surface uniformly.